Army Staff Sgt. Hilbert Caesar lost a leg in Iraq, serving a country that wasn't his.

His heart was American, but his passport said Guyana. That changed yesterday in a sweltering immigration office in Arlington. Four months after his Army convoy was devastated by a cluster of roadside bombs in Baghdad, Caesar became a U.S. citizen, walking into the ceremony with a cane and a powerful sense of optimism.

"I'm ecstatic. I can't even show the emotion," declared Caesar, who has been at Walter Reed Army Medical Center since April.

Caesar, 26, is one of thousands of immigrants in the military to become citizens since President Bush issued an order in July 2002 expediting their naturalization. About 32,400 noncitizens are serving in the armed forces, or roughly 2.3 percent of the total, according to Lt. Col. Ellen Krenke, a spokeswoman for the Department of Defense.

Immigrant soldiers have come into the spotlight as they have made the ultimate sacrifice for the country they serve. Thirty-eight noncitizens serving with the military have been killed in Afghanistan and Iraq, according to Krenke. One of the first members of the armed forces to die in combat in Iraq was Marine Lance Cpl. Jose Gutierrez, a native of Guatemala. He was posthumously awarded citizenship.

"Your choice to defend your country is . . . respected at the highest levels," Eduardo Aguirre, director of U.S. Citizenship and Immigration Services, told Caesar and several other members of the military at the ceremony yesterday.

Immigrants are allowed to join the armed forces as long as they are legal permanent residents, or green card holders. More than 16,000 have applied to become citizens since Bush's executive order, which allows them to apply for naturalization immediately instead of waiting three years, as previously required of immigrants in the military. Most civilians must wait five years.

Among the 34 who took the oath of citizenship at yesterday's ceremony were a Dominican serving as an Army administrator and a Jamaican-born Marine.

Two former soldiers who had been posted to Iraq -- a Salvadoran and a Jamaican -- also became citizens.

But Caesar was the star of the ceremony, a strapping man who walks with a slight limp. A casual observer might not even notice that one leg was not the one he started life with.

"You are a man of honor," Aguirre told Caesar. "I'm proud to soon call you a fellow citizen."

Caesar showed little emotion as he joined the immigrants from 27 countries in an off-tune rendition of "The Star-Spangled Banner" and raised his right hand to take the oath of citizenship. But when Aguirre finally said, "Congratulations, you're U.S. citizens!" Caesar could no longer contain himself.

"Hoo-ah!" he whooped -- the Army's cry of gung-ho commitment and approval.

In a news conference after the ceremony, Caesar said that when he was 11, his family emigrated from South America in search of opportunity. He spent his teens in New York and joined the Army at 20.

"I was born to be a soldier or a police officer," he said, adding later: "I love helping people. That's what American soldiers do."

He was working as a field artillery section chief with the 1st Armored Division when he and other soldiers set out along a road in Baghdad on April 18. They never saw the four explosive devices buried in the dirt. The explosion injured several other soldiers in addition to Caesar.

Caesar said he didn't want to focus on the bombing but on the future. He hopes to continue in the military, perhaps as a medical technician, or become a police officer.

While happy to be a citizen, Caesar said he felt no different.

"I knew I was an American before this," he said. "I always knew I was an American."

Staff writer Sarah Park contributed to this report.

Staff Sgt. Hilbert Caesar, a native of Guyana, is escorted at his naturalization ceremony in Arlington by Norine Han of the U.S. Citizenship and Immigration Services.Caesar, left, takes the oath of citizenship along with more than 30 other people.Besides Hilbert Caesar, left, those becoming citizens included a Dominican in the Army and a Jamaican Marine. An executive order sped the process for military members.